This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A306579 #31 Mar 16 2019 09:17:41
%S A306579 2,7,4,6,8,9,3,8,5,2,9,7,0,6,3,4,6,2,4,1,3,6,2,5,3,0,0,5,3,8,1,4,5,8,
%T A306579 5,7,5,7,8,9,9,8,8,6,5,4,3,1,2,7,7,7,0,5,4,1,2,8,1,8,6,3,6,2,8,0,3,1,
%U A306579 6,0,4,5,0,4,0,7,2,8,3,8,8,9,3,2,6,8,3,1,1,5,5,8,4,6,6,8,0,6,0,9,5,8,2,0,4,5,7,4,0,6
%N A306579 Decimal expansion of the real number x such that f(x) = x^x^x^x is a minimum.
%C A306579 It satisfies 1 + x^x*log(x)*(1 + x*log(x)*(1 + log(x))) = 0.
%C A306579 The function x^x has a minimum at x = 1/e (A068985).
%e A306579 0.274689385297063462413625300538145857578998865431277705412818636280...
%t A306579 n = 500;
%t A306579 (x /. FindMinimum[x^x^x^x, {x, 0.34}, WorkingPrecision -> 3 n][[2]][[1]] // RealDigits)[[1]][[;; n]]
%o A306579 (PARI) solve(x=0.1, 1, 1 + x^x*log(x)*(1 + x*log(x)*(1 + log(x)))) \\ _Michel Marcus_, Mar 15 2019
%Y A306579 Cf. A068985, A306883.
%K A306579 nonn,cons
%O A306579 0,1
%A A306579 _Philipp O. Tsvetkov_, Mar 15 2019